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bpo-32110: codecs.StreamReader.read(n) now returns not more than n #4499

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Merged
serhiy-storchaka merged 2 commits into from
Nov 28, 2017
Merged

bpo-32110: codecs.StreamReader.read(n) now returns not more than n #4499

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bpo-32110: codecs.StreamReader.read(n) now returns not more than n
serhiy-storchaka Nov 22, 2017
7ecbca3
Simplify the code.
serhiy-storchaka Nov 22, 2017
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8 changes: 5 additions & 3 deletions Lib/codecs.py
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Original file line number Diff line number Diff line change
Expand Up @@ -480,15 +480,17 @@ def read(self, size=-1, chars=-1, firstline=False):
self.charbuffer = self._empty_charbuffer.join(self.linebuffer)
self.linebuffer = None

if chars < 0:
# For compatibility with other read() methods that take a
# single argument
chars = size

# read until we get the required number of characters (if available)
while True:
# can the request be satisfied from the character buffer?
if chars >= 0:
if len(self.charbuffer) >= chars:
break
elif size >= 0:
if len(self.charbuffer) >= size:
break
# we need more data
if size < 0:
newdata = self.stream.read()
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18 changes: 16 additions & 2 deletions Lib/test/test_codecs.py
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Expand Up @@ -196,19 +196,33 @@ def getreader():
self.assertEqual(f.read(), ''.join(lines[1:]))
self.assertEqual(f.read(), '')

# Issue #32110: Test readline() followed by read(n)
f = getreader()
self.assertEqual(f.readline(), lines[0])
self.assertEqual(f.read(1), lines[1][0])
self.assertEqual(f.read(0), '')
self.assertEqual(f.read(100), data[len(lines[0]) + 1:][:100])

# Issue #16636: Test readline() followed by readlines()
f = getreader()
self.assertEqual(f.readline(), lines[0])
self.assertEqual(f.readlines(), lines[1:])
self.assertEqual(f.read(), '')

# Test read() followed by read()
# Test read(n) followed by read()
f = getreader()
self.assertEqual(f.read(size=40, chars=5), data[:5])
self.assertEqual(f.read(), data[5:])
self.assertEqual(f.read(), '')

# Issue #12446: Test read() followed by readlines()
# Issue #32110: Test read(n) followed by read(n)
f = getreader()
self.assertEqual(f.read(size=40, chars=5), data[:5])
self.assertEqual(f.read(1), data[5])
self.assertEqual(f.read(0), '')
self.assertEqual(f.read(100), data[6:106])

# Issue #12446: Test read(n) followed by readlines()
f = getreader()
self.assertEqual(f.read(size=40, chars=5), data[:5])
self.assertEqual(f.readlines(), [lines[0][5:]] + lines[1:])
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2017-11-22-09-44-15.bpo-32110.VJa9bo.rst
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@@ -0,0 +1,3 @@
``codecs.StreamReader.read(n)`` now returns not more than *n*
characters/bytes for non-negative *n*. This makes it compatible with
``read()`` methods of other file-like objects.